Concrete ties have been in use in some parts of the world for a long time but it is only since 1985 that they have been able to provide cost benefits for use in North America relative to wooden ties.
One advantage of concrete ties is that the rail seats can be pre assembled with only a few components to be added on site when the rail is placed in position. The difficulty with this is that the pre assembled components can become dislodged during transport and some components still have to be positioned on the rail. The rail seats usually comprise a rail pad that is positioned below the rail, an abrasion resistant plate below the pad, rail clip support shoulders on the field and gauge sides of the rail, an elastic rail clip that seats in the support shoulder and bears down on the rail base and an insulator that lies between the rail and the rail clip and the support shoulder. The support shoulders are precast in the rail tie and the rail pad is fitted between each pair. Because the rail clips and insulators contact the rail when fastened they cannot be placed in position until the rail has been placed in position on the rail seat. Rail seat assemblies of this type have been generally described in U.S. Pat. Nos. 5,110,046, 5,551,633 and 6,604,690. The rail clips in these assemblies are either installed or loose and therefore have to be assembled on site.
When new insulated railway track is being laid the ties are positioned first. Usually the rail pads are captive on the ties and sometimes the clips are also captive in the shoulders. Next the rail is threaded into the rail seats and the rail is centered in each seat and the insulators placed between the rail base edges and the shoulders. Finally the clips are pushed into the installed position.
U.S. Pat. No. 6,367,704 proposed using a modified support shoulder so that the clip could be partially installed for transport purposes where it was retained on the shoulder and then able to be fully installed when the rail was placed in position. In this arrangement the insulators still needed to be placed in position manually before the clip could be fully installed.
However it is difficult to position the rail exactly central in the rail seat so that the insulators can be fitted between the shoulders and the rail. This operation takes considerable manpower and time. In addition starting the clips by hand in readiness for the clip fitting machine also consumes time.
U.S. Pat. No. 5,520,330 discloses a bent rod rail clip with a two part insulator that enables the rail seat to be pre-assembled at the tie plant.
U.S. patent application No. 2008/0203181 discloses a system which divides the insulator into two parts. The first part is the shoulder insulator which separates the rail base edge from the shoulder and the second part is the clip toe insulator which is made captive on the clip toe. The clip and toe assembly is then made so it can be parked on the shoulder and also holds the shoulder insulators in place. The pad is also made captive in the rail seat.
With this arrangement all the rail fastening components can be assembled in the parked position at the tie plant and when the tie is delivered to the track the rail can be threaded into the rail seat and a machine used to install the clips thereby saving a lot of time previously used centering the rail and fitting the insulators and starting the clips.
However for this to be satisfactory the parked fastening system must be capable of guiding the rail into the rail seat if the rail is not presented exactly centrally which occurs very frequently.
The rail is stiff and heavy and capable of imparting a severe blow to the parked fastening system which can result in broken insulators. The blow from the rail is usually in a vertical or horizontal direction so with laterally applied clips it tends to knock them backwards out of the parked position or worse still breaks the insulator. This then takes considerable time to reposition the clips and replace the broken parts. When this occurs the replacement of insulators and clips can be time consuming and inefficient
It is an object of this invention to provide an insulator combination that is less liable to damage during assembly.